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b.) Provide equations of equivalent number of induced flashovers for different spans to the next arrester that are shown by Table B.2 on page 34 of IEEE Std 1410-1997.

Interpretation Response #1In general, there are several different models that can be used to derive the shielding factor. One is given in Equation 4, with an attractive radius of 14 times the pole height, raised to the 0.6 power, for the receptor zone to either side of the structure. For the 10-m line this attractive radius would be 56 m and for the 20-m line of objects the attractive radius is 84 m.

Another IEEE model uses a fixed exposed width based on the stroke current, using for example the model of (Striking Distance) = 10 times (stroke current in kA) raised to the 0.65 power. For a median 31-kA strike, this would give a fixed striking distance of 93 m.

The section on induced flashovers will be revised in the new version of IEEE 1410 to introduce new findings and conclusions from recent work around the world.